In order to acquire a better understanding of the mechanism of chemical carcinogenesis, we have initiated studies on the conformation of DNA and RNA in solution and their interactions with carcinogens and mutagens. The methods employed in these studies include nuclear magnetic resonance (NMR), circular dichroism (CD), electric linear dichroism (ELD), electrophoresis of circular DNA and potential energy calculation. The results obtained so far include: (l) observation of A- and B-form DNA conformation in solution in electric field, and that DNA conformation in solution, in the absence of electric field, possesses a coiled coil-like tertiary structure; (2) electrophoresis of circular DNA reveal that organic solvents and alkylated ammonium ions unwind, whereas metallic and ammonium ions as well as polyamines wind the DNA helix; and (3) potential energy calculations indicate that there are four stable conformations for dinucleoside phosphates in solution.